It is well known in the art that biological tissues can be sliced into thin sections on a microtome for subsequent microscopic examination by a pathologist, for example. In order to prepare the specimen for such slicing it must first be processed with several fluids to dehydrate the tissue, to clear the tissue with a suitable oil and then to infiltrate the tissue with a paraffin wax or a combination of wax and resinous material. This processing has been conveniently carried out by placing the specimen in a fluid-permeable capsule and successively submerging the capsule in the necessary fluids. The resulting processed specimen is then removed from the capsule and embedded in a block of paraffin wax for subsequent mounting in a microtome for slicing.
Generally the capsule apparatus employed for the tissue processing is separate from the apparatus employed for embedding the specimen in paraffin. U.S. Pat. No. 3,674,396 (now U.S. Reissue Pat No. 28,165)describes improved apparatus wherein an open- -topped box-like perforated mold member having a perforated removable cover can be used with the cover in place as a tissue processing capsule and with cover removed can be used for embedding a specimen in paraffin. The apparatus described in the above prior art patent had the disadvantage that the volume of the processing apparatus could not be adjusted to compensate for different sized specimens. There is a commercial need for combination processing-embedding apparatus that is adjustable for such different sized specimens. There is also a commercial need for an adjustable cover to be used with the apparatus of the above prior art patent.